/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_sparse_f32.c
*
* Description:	Floating-point sparse FIR filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
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*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
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*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* ------------------------------------------------------------------- */
#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @defgroup FIR_Sparse Finite Impulse Response (FIR) Sparse Filters
 *
 * This group of functions implements sparse FIR filters.
 * Sparse FIR filters are equivalent to standard FIR filters except that most of the coefficients are equal to zero.
 * Sparse filters are used for simulating reflections in communications and audio applications.
 *
 * There are separate functions for Q7, Q15, Q31, and floating-point data types.
 * The functions operate on blocks  of input and output data and each call to the function processes
 * <code>blockSize</code> samples through the filter.  <code>pSrc</code> and
 * <code>pDst</code> points to input and output arrays respectively containing <code>blockSize</code> values.
 *
 * \par Algorithm:
 * The sparse filter instant structure contains an array of tap indices <code>pTapDelay</code> which specifies the locations of the non-zero coefficients.
 * This is in addition to the coefficient array <code>b</code>.
 * The implementation essentially skips the multiplications by zero and leads to an efficient realization.
 * <pre>
 *     y[n] = b[0] * x[n-pTapDelay[0]] + b[1] * x[n-pTapDelay[1]] + b[2] * x[n-pTapDelay[2]] + ...+ b[numTaps-1] * x[n-pTapDelay[numTaps-1]]
 * </pre>
 * \par
 * \image html FIRSparse.gif "Sparse FIR filter.  b[n] represents the filter coefficients"
 * \par
 * <code>pCoeffs</code> points to a coefficient array of size <code>numTaps</code>;
 * <code>pTapDelay</code> points to an array of nonzero indices and is also of size <code>numTaps</code>;
 * <code>pState</code> points to a state array of size <code>maxDelay + blockSize</code>, where
 * <code>maxDelay</code> is the largest offset value that is ever used in the <code>pTapDelay</code> array.
 * Some of the processing functions also require temporary working buffers.
 *
 * \par Instance Structure
 * The coefficients and state variables for a filter are stored together in an instance data structure.
 * A separate instance structure must be defined for each filter.
 * Coefficient and offset arrays may be shared among several instances while state variable arrays cannot be shared.
 * There are separate instance structure declarations for each of the 4 supported data types.
 *
 * \par Initialization Functions
 * There is also an associated initialization function for each data type.
 * The initialization function performs the following operations:
 * - Sets the values of the internal structure fields.
 * - Zeros out the values in the state buffer.
 * To do this manually without calling the init function, assign the follow subfields of the instance structure:
 * numTaps, pCoeffs, pTapDelay, maxDelay, stateIndex, pState. Also set all of the values in pState to zero.
 *
 * \par
 * Use of the initialization function is optional.
 * However, if the initialization function is used, then the instance structure cannot be placed into a const data section.
 * To place an instance structure into a const data section, the instance structure must be manually initialized.
 * Set the values in the state buffer to zeros before static initialization.
 * The code below statically initializes each of the 4 different data type filter instance structures
 * <pre>
 *arm_fir_sparse_instance_f32 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q31 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q15 S = {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 *arm_fir_sparse_instance_q7 S =  {numTaps, 0, pState, pCoeffs, maxDelay, pTapDelay};
 * </pre>
 * \par
 *
 * \par Fixed-Point Behavior
 * Care must be taken when using the fixed-point versions of the sparse FIR filter functions.
 * In particular, the overflow and saturation behavior of the accumulator used in each function must be considered.
 * Refer to the function specific documentation below for usage guidelines.
 */

/**
 * @addtogroup FIR_Sparse
 * @{
 */

/**
 * @brief Processing function for the floating-point sparse FIR filter.
 * @param[in]  *S          points to an instance of the floating-point sparse FIR structure.
 * @param[in]  *pSrc       points to the block of input data.
 * @param[out] *pDst       points to the block of output data
 * @param[in]  *pScratchIn points to a temporary buffer of size blockSize.
 * @param[in]  blockSize   number of input samples to process per call.
 * @return none.
 */

void arm_fir_sparse_f32(
    arm_fir_sparse_instance_f32 *S,
    float32_t *pSrc,
    float32_t *pDst,
    float32_t *pScratchIn,
    uint32_t blockSize)
{

    float32_t *pState = S->pState;                 /* State pointer */
    float32_t *pCoeffs = S->pCoeffs;               /* Coefficient pointer */
    float32_t *px;                                 /* Scratch buffer pointer */
    float32_t *py = pState;                        /* Temporary pointers for state buffer */
    float32_t *pb = pScratchIn;                    /* Temporary pointers for scratch buffer */
    float32_t *pOut;                               /* Destination pointer */
    int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
    uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
    uint16_t numTaps = S->numTaps;                 /* Number of filter coefficients in the filter  */
    int32_t readIndex;                             /* Read index of the state buffer */
    uint32_t tapCnt, blkCnt;                       /* loop counters */
    float32_t coeff = *pCoeffs++;                  /* Read the first coefficient value */



    /* BlockSize of Input samples are copied into the state buffer */
    /* StateIndex points to the starting position to write in the state buffer */
    arm_circularWrite_f32((int32_t *) py, delaySize, &S->stateIndex, 1,
                          (int32_t *) pSrc, 1, blockSize);


    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if(readIndex < 0)
    {
        readIndex += (int32_t) delaySize;
    }

    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                         (int32_t *) pb, (int32_t *) pb, blockSize, 1,
                         blockSize);

    /* Working pointer for the scratch buffer */
    px = pb;

    /* Working pointer for destination buffer */
    pOut = pDst;


#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    /* Loop over the blockSize. Unroll by a factor of 4.
     * Compute 4 Multiplications at a time. */
    blkCnt = blockSize >> 2u;

    while(blkCnt > 0u)
    {
        /* Perform Multiplications and store in destination buffer */
        *pOut++ = *px++ * coeff;
        *pOut++ = *px++ * coeff;
        *pOut++ = *px++ * coeff;
        *pOut++ = *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4,
     * compute the remaining samples */
    blkCnt = blockSize % 0x4u;

    while(blkCnt > 0u)
    {
        /* Perform Multiplications and store in destination buffer */
        *pOut++ = *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* Load the coefficient value and
     * increment the coefficient buffer for the next set of state values */
    coeff = *pCoeffs++;

    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if(readIndex < 0)
    {
        readIndex += (int32_t) delaySize;
    }

    /* Loop over the number of taps. */
    tapCnt = (uint32_t) numTaps - 2u;

    while(tapCnt > 0u)
    {

        /* Working pointer for state buffer is updated */
        py = pState;

        /* blockSize samples are read from the state buffer */
        arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                             (int32_t *) pb, (int32_t *) pb, blockSize, 1,
                             blockSize);

        /* Working pointer for the scratch buffer */
        px = pb;

        /* Working pointer for destination buffer */
        pOut = pDst;

        /* Loop over the blockSize. Unroll by a factor of 4.
         * Compute 4 MACS at a time. */
        blkCnt = blockSize >> 2u;

        while(blkCnt > 0u)
        {
            /* Perform Multiply-Accumulate */
            *pOut++ += *px++ * coeff;
            *pOut++ += *px++ * coeff;
            *pOut++ += *px++ * coeff;
            *pOut++ += *px++ * coeff;

            /* Decrement the loop counter */
            blkCnt--;
        }

        /* If the blockSize is not a multiple of 4,
         * compute the remaining samples */
        blkCnt = blockSize % 0x4u;

        while(blkCnt > 0u)
        {
            /* Perform Multiply-Accumulate */
            *pOut++ += *px++ * coeff;

            /* Decrement the loop counter */
            blkCnt--;
        }

        /* Load the coefficient value and
         * increment the coefficient buffer for the next set of state values */
        coeff = *pCoeffs++;

        /* Read Index, from where the state buffer should be read, is calculated. */
        readIndex = ((int32_t) S->stateIndex -
                     (int32_t) blockSize) - *pTapDelay++;

        /* Wraparound of readIndex */
        if(readIndex < 0)
        {
            readIndex += (int32_t) delaySize;
        }

        /* Decrement the tap loop counter */
        tapCnt--;
    }

    /* Compute last tap without the final read of pTapDelay */

    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                         (int32_t *) pb, (int32_t *) pb, blockSize, 1,
                         blockSize);

    /* Working pointer for the scratch buffer */
    px = pb;

    /* Working pointer for destination buffer */
    pOut = pDst;

    /* Loop over the blockSize. Unroll by a factor of 4.
     * Compute 4 MACS at a time. */
    blkCnt = blockSize >> 2u;

    while(blkCnt > 0u)
    {
        /* Perform Multiply-Accumulate */
        *pOut++ += *px++ * coeff;
        *pOut++ += *px++ * coeff;
        *pOut++ += *px++ * coeff;
        *pOut++ += *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* If the blockSize is not a multiple of 4,
     * compute the remaining samples */
    blkCnt = blockSize % 0x4u;

    while(blkCnt > 0u)
    {
        /* Perform Multiply-Accumulate */
        *pOut++ += *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

#else

    /* Run the below code for Cortex-M0 */

    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
        /* Perform Multiplications and store in destination buffer */
        *pOut++ = *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

    /* Load the coefficient value and
     * increment the coefficient buffer for the next set of state values */
    coeff = *pCoeffs++;

    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if(readIndex < 0)
    {
        readIndex += (int32_t) delaySize;
    }

    /* Loop over the number of taps. */
    tapCnt = (uint32_t) numTaps - 2u;

    while(tapCnt > 0u)
    {

        /* Working pointer for state buffer is updated */
        py = pState;

        /* blockSize samples are read from the state buffer */
        arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                             (int32_t *) pb, (int32_t *) pb, blockSize, 1,
                             blockSize);

        /* Working pointer for the scratch buffer */
        px = pb;

        /* Working pointer for destination buffer */
        pOut = pDst;

        blkCnt = blockSize;

        while(blkCnt > 0u)
        {
            /* Perform Multiply-Accumulate */
            *pOut++ += *px++ * coeff;

            /* Decrement the loop counter */
            blkCnt--;
        }

        /* Load the coefficient value and
         * increment the coefficient buffer for the next set of state values */
        coeff = *pCoeffs++;

        /* Read Index, from where the state buffer should be read, is calculated. */
        readIndex =
            ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

        /* Wraparound of readIndex */
        if(readIndex < 0)
        {
            readIndex += (int32_t) delaySize;
        }

        /* Decrement the tap loop counter */
        tapCnt--;
    }

    /* Compute last tap without the final read of pTapDelay */

    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_f32((int32_t *) py, delaySize, &readIndex, 1,
                         (int32_t *) pb, (int32_t *) pb, blockSize, 1,
                         blockSize);

    /* Working pointer for the scratch buffer */
    px = pb;

    /* Working pointer for destination buffer */
    pOut = pDst;

    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
        /* Perform Multiply-Accumulate */
        *pOut++ += *px++ * coeff;

        /* Decrement the loop counter */
        blkCnt--;
    }

#endif /*   #ifndef ARM_MATH_CM0_FAMILY        */

}

/**
 * @} end of FIR_Sparse group
 */
